Method of grinding threads



' J. BATH METHOD OF GRINDING ,THREADS 2 Sheets-s 1 Original Filed Dec.27, 1921 L ho.

Jan. 29, 1929.

J. BATH METHOD OF GRINDING THREADS 8 vweufoz Hozn 3 2 Sheets-Sheet 2llllllLlnlull-l'lulllll'l Original Filed Dec. 27, 1921 w mw vlo

Patented Jan. 29, 1929.

entree era-res toxin BATH, or wonon's rsn,MAssAeHusETrs.

METHOD or eRI-NninG rnREAns.

" Original application filed December 27, 1921, Serial No.'52 4,817.innate and th isappl icatio n filed July Y 13,1925. Serial No. 43,418. a

This invention relates to amethod of grinding threads and isa divisionof my prior ap- Tplication, Serial No; 5524;817', filed December 27,1921and-patentedFebruary 28, 1928, No. 1,660,468. Y

It is thegeneral object of mypresent invention to i provide a method ofgrinding threads on taps, thread-gauges, screws, and similar articles bywhich the operation of themachine may be made substantially continuous,with the grinding wheel acting on the work in both directionsof axialtravel.

In the attainment of thisv object I provide a novel sequenceofoperationsby which'the back lash of the machine is taken up at thecompletion of each cut by the grinding Wheel in each direction and bywhich the wheel is accurately alignedwith the preceding cut tuponitsreturn travel. V

Y My invention further. relates to certain details of operation whichwill be hereinafter described andmoreparticularly pointed out"intheappendedclaims. Y

A form of mechanism suitable for the carrying out of my improved methodis shown in the drawings, 1n which y Fig. 1 1s an end elevatlon of adrlving spindle and work driving attachments thereon adapted for provedmethod; I I i Y Fig. 2 is asectional elevation taken along the line 22in Fig. l;

Fig. 3 is aipartial plan view looking in'the direction of the arrow 3 inFig. 2;

Y taken respectively along the lines4-4 5-5,

6-6, 77 of Fig. 1; I

-Fig.'8 is a plan view of certain parts ofthe' machine, illustrating theprocedure by which the amount of backlash is determined Fig. 9 is adetail sectional elevation taken along the line 99 in Fig. 8; and

Y Fig. 10 is an'end elevation looking in the direction of the arrow 10in Fig. 8;

Referring particularly to Figs. 1 and 81 have shown'parts of a threadgrinding machine including a head'center'mounted in a spindle rotatablein bearings in a head mounted in a tail stock 93. A grinding wheel W ismounted on awheel shaft 37 rotatably supported 'on a'wheel table 34slidable on a .IIiOUIltQd. A ma es is slidablyadjustable in plicationabove identified.

'ters of the machine. the carrying out of my 1111- 111 'isfshown asextending through this slot,

Figs. 4 5, 6 and? are detail sectionalviews I while the screw 112extends through a hole in guideways 49 and '50 in the wheel table" andmay be clamped thereto by bolts 51. .A lead screw 46 is rotatablein'afiXed'beari-ng. 47

and engages the nut 48 to reciprocateth'e vwheelta ble. The screw '46 isconnected to rotate wlththe spindle 60 by a train ofgears .56, 57 and 58so thateach rotation ofthe spindle and work corresponds to a definiteaxial movement of the wheel. 5 For .a more complete description of theparts above referred to, reference is made to the prior ap Intheoperation of my improved grinding Y 'inacliine, I use work, drivingdevicesof novel construction which devices will now be de- 'scr1'bedparticular reference being made to 0 Figs. 2 to 7.

The usual face plate is threaded onthe end of the spindle 60 andisprovided with a hub or extension 106'on which is mounted a' ring 107supporting apair'of work driving 'dogs 108. These dogs'are radiallyjadjustable on the ring'107 and/are; secured thereto by binding screws109.; The inner ends of the dogs are shaped to 'receive and engage" thewhichis mouhted'onthe head and tail cen- The ring107 is flanged andisheld against,

the face plate by an outerring110"securedi to the faceplate bybindingscrews 111 and v 112 (Figs. 1 and 7) A slot 113 extends nearly aroundthe ring 110 and the binding screw tionsll'? (Fig. 6): fitting thesegmental slot 113. These blocks are "secured in 'iangular adjustedpositionby clamping bolts "118 and nuts 119 (Fig. 5). A springhandle'120 is secured to each-"block or 116 a 'nd is.provided with aspur 121' engagingnotches 110 Y I formed at the outeredge oftheringillO. f stock 32 and also including a tail center 90 l A similarspring handle 1'22is se'curedtothe inner ring 107 ,this handle beingprovided with a socket or recesszl23 adapted toreceive pins" or "studs124 formed dnxtheends of the bolts 118 which secure the blocks 1.15'and-116 in position. Sto{ps;125 and-126:;(Figsn1-and 4) are alsoslidable inthe slot 113 of thering so I shank of a tap or other articleto be ground 110 andmaybe clamped in position as will theback lash inthe connections between the work spindle and the grinding wheel table.The extent of this angular adjustment .of thework required with aparticular set-up of the machine is determined experimentally by useofthe indicating device shown in Figs. 8to10. I

' An arm130 (Fig. 8) is fixed on the lead screw nut 4:8 and-extendsforwardly and upwardly to a position for engagement by the .shortend ofan index lever 131, pivoted at .132 on a stand 133. The stand isadjustably secured'to thehead stock 32 bya clamping bolt 1341. Alockplate 135 is slidably mounted in guideways 1 36 on the head stock 32i and may be secured in adjusted position by a clamping bolt 137. Anindex or zero line is formed on one of the guide-ways136 as a referencemark for-the index lever 131.

coincides .with way136.-. i

In order to determine the exact amount of back lashin the connectionsbetween the spindle and the-wheel table, the spindle is moved .in thedirection in which it has been rotating ,until the handle 1220f the dogsupporting ring 107 is aligned with the jaws of the lock plate 135..This plate is then advanced in itsguideways 136 until it releases thehandle 'from the pin or stud 124 on which it has been seated and looksit from further angular, movement. The stand 133 ofthe index lever orpointer 131 is then adjusted so that the rearend 01": the pointer willbe pressed against the arm 130 by thepointer spring 138, while at thesame'time the other end of the pointer the zero mark on the guidevThespindle is then turned backward or in the oppositedirection to that inwhich I it has been rotating until the lead screw 46 begins to move. thenut 48, such movement being instantly indicated by movement of thepointer 131. The second sliding block 115 or 116 is then moved to bringits stud124 into alignment with the recess in the handle 122, in whichposition it is then secured.

1 ith'the positionsof the blocks 115 and i 116 thus. accurately located,it is -merely necessary to'swing the handle 1 22 from one :stud 124C tothe other, when the direction of the table teedis reversed to cause thegrinding wheel to accurately follow the thread in 1 both directions oftable feed. If it is found that .the :wheel when thus adjusted engagesslightly harder on one side than 'on the other,

- one'of-theblocks 115 or 116 may be further adjusted by. moving itshandle 120 one: or

more notches along the ring 110. -VVhen adjustment is once-made for aparthe connections between the ticular set-up of the machine, no furtherattention is necessary beyond. swinging the handle .122 from one stud124 to the other at each end of the wheel travel. The output of themachine is thus greatly increased, as the usual idle return feed of thegrlndlng wheel is entirely avoided.

When grinding certainetypes of thread, such asthe Acme thread, itissometimes desirable to feed the wheel sideways to widen the threadgroove. The stops 125 and .126 are-th on used to preserve the originalsetting so that the slides115'0r 116 maybemovedf the required number otnotchessideways to widen the thread and may then bewreturned to theiroriginal positions when a new thread is to be ground and widened. J

The face plate 105 may be providedwith graduations as shown in Fig. 3andthe ring 110 may have an index mark cooperating therewith to indicatethe angularirelation of these parts. These graduations areuseful when itis desired to advance the ring a certain angular amount relative to theface plate. r Y.

I Having thus described my improved met/h od it will be seen that thismethod renders the grinding operation substantially contins uous andentirely eliminates theyidlereturn run of the wheel which hasbeen' theusual prior practice. I am also-able to'take up the back lash by a verysimple manual operation after a machine has once been set for the workto be ground andthe output'ot the machine is very greatly increased overthe amount of work which can be done when grinding in one directiononly.1

This method of grinding has been particularly described with reference-to-' grinding taps but it is to be understood that the method .isequally applicable to grinding screws,

worms, thread gauges and any other articles of a similar nature in whichthreadsor helical grooves are to be produced by grinding. Having thusdescribed my invention and the advantages thereofI do not wish to belimited to the details herein disclosed other: wise than as set forthin-the claimsbut what I claim is 1. The method of grinding threads whichcomprisestaking a grinding cut with the work rotating in one direction,makinga'relative adjustment of parts between the work and the wheelequivalent to the back lash in Work and wheel, and then taking a secondcut over the same threads with the direction of rotation of the workreversed and with thewheel moving axially along the work ina directionreversed to that of the firstdescribed cut, the

direction of wheel 'ieed reversed.

comprises taking-a grinding, cut with the work rotating in onedirection, angularly adjusting the work a-definite predetermined.

' amount, and taking a second cut with the work rotating in the oppositedirection.

3. The method. of grinding threads which comprises taking a grinding outWith the work rotating in one direction, adjusting the vwork an amountequivalent to the back lash between the Work and the wheel, and takingwork rotating in one direction, angularly ad, I .justing the workrelatively to-the spindle an amount equal to the back lash between thework and the wheel, and thereafter taking 15 a second cut with the workrotating in the opposite direction, the wheel remaining in positionadvanced toward thework during all steps of the operation.

In testimony whereof I fixed my signature.

JOHN BATH.

have hereunto af-

